### Trains

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## Trains

Formulae

1. Speed =
Time
Distance
S =
S
D

2. Time taken by a train x meters long to pass a pole or standing man or a post = Time taken by the train to travel x meters.

3. Time taken by a train x meters long to pass an object of length y meters = Time taken by the train to travel (x + y) metres.

4. Suppose two trains or two objects are moving in the same direction at v1 m/s and v2 m/s where v1 > v2, then their relative speed =
(v1 - v2) m/s

5. Suppose two trains or two objects are moving in opposite directions at v1 m/s and v2 m/s, then their relative speed =
(v1 + v2) m/s

6. Assume two trains of length x metres and y metres are moving in opposite directions at v1 m/s and v2 m/s, Then the time taken by the trains to cross each other =
(x+y) / (v1+v2) seconds

7. Assume two trains of length x metres and y metres are moving in the same direction at at v1 m/s and v2 m/s where v1 > v2, Then the time taken by the faster train to cross the slower train =
(x+y) / (v1-v2) seconds

8. Assume that two trains (objects) start from two points P and Q towards each other at the same time and after crossing they take p and q seconds to reach Q and P respectively. Then,
A's speed: B's speed = √ q : √ p